Use of a hydrocarbon fluid over 2 psi Reid vapor pressure (RVP) is restricted for use in hydraulic fracturing without written permission from regulators. Also, if the flash point is 0 C or less it is a special consideration fluid. Both RVP and Flash point drive the classification of high Reid vapor pressure (HRVP) fluids. A conventional open tub blender could not be used with HRVP hydrocarbons. Accordingly, there is a means of enclosing a blender tub to enable HRVP fluids to be used.
U.S. Patent Application No. 2007/0204991 discloses a proppant mixing system that relies on a spinning impeller mixing frac fluid with proppant to generate a dynamic seal. A continuous flow of proppant is allowed through a check valve and control valve. However, the tub is not adequately enclosed, particularly between the tub and the auger.